Lithologic Reservoirs

The control of high resolution sequence stratigraphy on the vertical distribution of sedimentary microfacies and reservoirs in upperMa 5 member of Majiagou Formation in Tong 5 well block of Jianbian Gas Field in Ordos Basin is studied. Ma 5 1- 4 submember is an asymmetric long-term base level cycle which can be divided into five middle-term base level cycles and more than 26 short-termbase level cycles. The study result shows that the sedimentarymicrofacies and reservoirs of Ma 5 member of Majiagou Formation in Tong 5 wellblock of Jingbian Gas Field are probably dominated by long-term base level cycle. The control action of middle-term and short-term base level cycles on the distribution of sedimentary microfacies and reservoirs is distinguished. Middle-term and short-term base level cycles control the vertical subtle change of sedimentary microfacies of carbonate tidal flat in continental sea tableland, and control the vertical distribution of vugular dolomite reservoir ofweathered crust. It is feasible to divide the cycles ofMa 5 1- 4 by high resolution sequence stratigraphy. The achievement of this research can be applied to the analogous reservoir studies in other areas.

A type of specific subtle reservoir : Analysis on the origin of diagenetic trapped reservoirs and its significance for exploration in Xia 9 wellblock of Junggar Basin

KUANG Hongwei, GAO Zhenzhong, WANG Zhengyun, WANG Xiaoguang

2008, Vol.20(1): 8–14 Abstract ( 483 ) PDF (599 KB) ( 607 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.002

The geological setting of Xia 9 wellblock is a nose structure which uplifted and disappeared toward northeast direction with no structural trap and up dip wedge out trap. Several different scale reservoirs were discovered in the lower part of this nose structure in the Triassic and Jurassic strata. To a same sand body, the lower part of the structure is oil layer; however, the higher part of the structure is water layer. This abnormal phenomenon has been an enigma for a long time. Recently, based on the actual data and research, it is considered that diagenetic shading is the key factor in controlling the distribution of the reservoirs in Xia 9 wellblock, and that the structural break slope is an essential condition for the forming of diagenetic shading. The intensity of diagenetic shading is closely related to physical properties of reservoir. The accumulation scale of this diagenetic trapped reservoir is inversely correlated with the physical properties. The discovery and the understanding of the diagenetic trapped reservoirs in Xia 9 wellblock provide a newtarget for oil and gas exploration.

“Multi-factor controlling, four-factor entrapping and key-factor enrichment”of stratigraphic-lithologic reservoirs and exploration practice in Erlian Basin (Ⅳ)———Exploration practice

HAN Chunyuan,ZHAO Xianzheng,JIN Fengming,WANG Quan,LI Xianping,WANG Suqing

2008, Vol.20(1): 15–20 Abstract ( 567 ) PDF (532 KB) ( 498 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.003

Based on four typical examples of successful exploration for stratigraphic-lithologic reservoirs in Erlian Basin, the research on the accumulation mechanism of “Multi-factor controlling, four-factor entrapping and key-factor enrichment”of stratigraphic-lithologic reservoirs is deepened, and newaccumulation models of stratigraphic-lithologic reservoirs are established. The result shows that petroleum exploration has made a significant breakthrough. Four stratigraphic-lithologic reservoir blocks with reserves of 30 to 50 million tons have been discovered successively in Bayindulan Sag,Wuliyasitai Sag, Jiergalangtu Sag and Saihantala Sag.

Comprehensive evaluation method for sealing ability of mudstone caprock to gas in each phase

FU Guang, LIU Bo, LV Yanfang

2008, Vol.20(1): 21–26 Abstract ( 541 ) PDF (347 KB) ( 555 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.004

Based on the study on sealing mechanisms of mudstone caprock to gas in each phase, the percolation and diffusion velocity of gas in free phase, water-dissolving phase and diffusive phase through mudstone caprock under the action of imposed pressure and gas-bearing concentration are applied to establish the evaluation parameters (Vs, Vw and Vd) for sealing ability of mudstone caprock to gas in free phase, in water-dissolving phase and in diffusive phase respectively. And then, a comprehensive evaluation method for sealing ability of mudstone caprock to gas in each phase is established by weighted average value. This method is applied to evaluate the sealing ability of mudstone caprock to gas in each phase of Qingshankou Formation in Binbei area. The result shows that the mudstone caprock of Qingshankou Formation is of middle sealing ability, and poor sealing ability in Nehe and eastern Suileng. Poor sealing ability is one of the main factors which caused the poor gas shows in this area.

Study on fluid inclusion of tight sandstone reservoir of Upper Triassic Xujiahe Formation in central Sichuan Basin

LI Yun, SHI Zhiqiang

2008, Vol.20(1): 27–32 Abstract ( 507 ) PDF (393 KB) ( 659 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.005

The petrography and temperature measurement of fluid inclusions are analyzed. The result shows that there exist fluid inclusions of early and late stages in tight sand reservoir of Upper Triassic Xujiahe Formation in central Sichuan Basin. The homogenization temperature of the early stage fluid inclusions is low, mainly of 80 ～100℃, while the homogenization temperature of the late stage fluid inclusions is higher, mainly of 120～140℃. It is concluded that hydrocarbon accumulation and migration in tight sand reservoir in central Sichuan Basin experienced the Late Jurassic and Late Cretaceous-early Paleogene, which is accordant with the result derived from the saturation pressure of hydrocarbon reservoirs.

Concept and techniques of seismic geomorphology

JIANG Ren, FAN Tailiang, XU Shouli

2008, Vol.20(1): 33–38 Abstract ( 602 ) PDF (567 KB) ( 638 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.006

Seismic geomorphology is a newly developed interdisciplinary. It uses amplitude attribute extracted from 3D seismic data and 3D visualization images to study subsurface geology. This discipline, together with seismic lithology, composes the main parts of seismic sedimentology. The current developing status of this discipline is discussed, and a set of available work flow is proposed. Several techniques are applied in the study to carry out the imaging and visualization for depositional elements and geologic features, including slicing technique, seismic attributes analysis technique, coherence technique and 3D visualization technique. With the widespread application of high resolution 3D seismic data, seismic geomorphology will be developed rapidly.

Sequence-based lithofacies and paleogeography mapping of Paleogene in Lvda area, Liaodongwan Basin

DAI Chaocheng, ZHENG Rongcai, WEN Huaguo, ZHANG Xiaobing

2008, Vol.20(1): 39–46 Abstract ( 487 ) PDF (710 KB) ( 376 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.007

According to the data of cores, logging and some seismic data, under the guidance of the theory of highresolution sequence stratigraphy, the Paleogene is divided into two super long-term sequence cycles, 6 long-term sequence cycles, 18 middle-term sequence cycles and some dozens of short-term sequence cycles. Based on interfaces and structure characteristics, by selecting the rising and falling base-level phases of each long-term sequence cycle as the isochronous mapping unit, the sequence-based lithofacies and paleogeography maps are drawn. The evolution rule is deduced: during the phase of LSC2 and LSC3, the primary depositional environments are shallow lake and sublacustrine turbidite fan; sublacustrine turbidite fan and delta are developed during the phase of LSC4; and during the phase of LSC5 and LSC6, delta and shallowlake become prevalent. Frombottomto top, shallowlake, sublacustrine turbidite fan and delta depositional configuration formed, and the sand body extended, which can provide basis for forecasting reservoir sand body.

The origin of carbonate cements and the influence on reservoir quality of Pinghu Formation in Xihu Sag, East China Sea

ZOU Mingliang, HUANG Sijing, HU Zuowei, FENG Wenli, LIU Haoniannian

2008, Vol.20(1): 47–52 Abstract ( 499 ) PDF (588 KB) ( 509 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.008

Carbonate cements are the most abundant authigenic minerals in the reservoir sandstone of Pinghu Formation in Xihu Sag, East China Sea Basin. The analyses on thin section, cathodoluminescence, and elemental composition and carbon isotope showthat siderite, ankerite and calcite are the main minerals of the carbonate cements in Pinghu Formation. The siderite cement is mainly generated from syngenesis to early diagenesis, with highest δ13C ( 0.75‰) and δ18O ( - 10.22‰) . The δ13C of ankerite varies from - 2.45‰ to - 2.98‰, which is concordant with the coeval sea water, and the δ18O of ankerite is low, with least of - 12.39‰, and occurs during the early diagenetic stage. Granular and poikilitic cementations are the main occurrences of calcite cement. Granular calcite has many origins; however, the origin of the poikilitic calcite cement is closely related to the aluminosilicate minerals and the transformation of clay minerals. The siderite and ankerite precipitated in the early diagenetic stage enhanced the mechanical strength of rock and resistance to compaction, which is favorable for the reservoir quality, while the intergrowth calcite cementation generated in the late period is disadvantageous for the reservoir quality.

High resolution sequence stratigraphy framework and the distribution of sandbodies in salt lake of Qianjiang Formation in Zhongshi Oilfield

YIN Yanshu, ZHANG Shangfeng, YIN Taiju

2008, Vol.20(1): 53–58 Abstract ( 471 ) PDF (901 KB) ( 440 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.009

The high resolution sequence stratigraphy of salt lake in the third member of Qianjiang Formation in Zhongshi Oilfield is studied. Based on the characteristics of scoured surface, flooding surface and the rock salt boundary surface, and the facies association, three short-term base level cycles are identified, including deepening upward asymmetry base level cycle, shallowing-upward asymmetry base level cycle, and symmetry base level cycle. According to the stacked pattern, the third member of Qianjiang Formation is divided into five middle-term base level cycles and one long-term base level cycle. The distribution of sand bodies is controlled by the ratio of accommodation to supply (A/S) . When A/S is very smaller than 1, the sand bodies are best developed, with best formation communication, and under the condition that the weather is hot and the lake evaporation is greater than the supply, the salt is deposited. When A/S is close to 1, the sand bodies are relatively developed. When A/S is very greater than 1, the sand bodies are undeveloped.

Study on the sedimentary facies of the member 3 and 4+5 of Yanchang Formation in Jiyuan area

SHI Xuefeng, DU Haifeng

2008, Vol.20(1): 59–63 Abstract ( 569 ) PDF (298 KB) ( 531 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.010

Jiyuan area, in southern Ordos Basin, is located at the structure unit between Shanbei Slope and Tianhuan Depression. The exploratory degree is low here, thus, the study on depositional system, sedimentary facies, reservoir distribution, traps accumulation, and the hydrocarbon enrichment of the member 3 and 4+5 of Yanchang Formation is not enough. Based on the outcrop, core and well log data, the lithologic characteristics, well log form and sedimentary microfacies are analyzed. The result shows that the member 3 and 4+5 are mainly composed of delta and lacustrine depositional systems, which can be further divided into two subfacies and five microfacies. According to the distribution and evolution rule of the sedimentary microfacies, the depositional model of the study area can be obtained.

Structural features of contemporaneous thrust faults in Hongche fault belt of Junggar Basin

YAN Shibang, HUWangshui, LI Ruisheng, GUAN Jian, LI Tao, NIE Xiaohong

2008, Vol.20(1): 64–68 Abstract ( 562 ) PDF (277 KB) ( 429 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.011

Hongche fault belt in northwest margin of Junggar Basin is divided into four fault subzones, including Hongshanzui thrust fault, Zhongguai thrust fault, Chepaizi thrust fault in NS direction and Che 75-Che 77 well thrust fault in NWdirection. The plane distribution and formingmechanismof each thrust fault are analyzed. The growth index and fault throw are applied to study the typical structural section. The result shows that most of the contemporaneous thrust faults are main front faults and high angle imbricate thrust structures with basement involvement. The contemporaneous thrust faults are considered to be closely related to the deposits in the Permian, Triassic and Jurassic bottom. The thrust-napping was intense in Permian, as a result, the thrust faults developed universally. The developing degree of the faults in Triassic weakened fromnorth to south. While in Jurassic, the faults developed well in the middle part and poor in north part, and stopped developing in south part of this area. From Permian to Triassic, the development of the contemporaneous thrust faults is piggyback propagation, and it is overstep propagation fromTriassic to Jurassic.

Migration and accumulation mechanism of sand lens reservoirs and its main controlling factors

MA Zhongliang, ZENG Jianhui, ZHANG Shanwen, WANG Yongshi,WANG Hongyu, LIU Huimin

2008, Vol.20(1): 69–74 Abstract ( 505 ) PDF (1872 KB) ( 553 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.012

Sand lens reservoir is the main type of lithologic reservoirs for increasing reserves, but its migration and accumulation mechanism is not understood well. The result of 2D physical experiment shows that the physical property of sand lens is closely related to its accumulation, and the oil saturation of sand lens reservoirs varies consistently with the change of the porosity and permeability. Oil always migrates from high potential zone to low potential zone and accumulates in the sealed low potential zone. Fluid potential determines whether sand lens can be input by oil or not. Physical properties and fluid potential are the two main controlling factors for the accumulation of sand tens reservoirs.

Activity analysis of main faults in Qianquan area, Banqiao Sag

WANG Bingjie, HE Sheng, NI June, FANG Du

2008, Vol.20(1): 75–82 Abstract ( 431 ) PDF (637 KB) ( 694 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.013

Based on the interpretation to Es3, Es2, lower Es1, middle Es1, upper Es1 and the bottom of Ed in Qianquan area, Banqiao Sag, the plane distribution of the faults is analyzed. The growth index, activity rate and paleo fall of fault are applied to study the fault activity. The result shows that there developed two vertical normal faults towards NE and NW respectively in Qianquan area, among which Cangdong fault is first order fault, Dazhangtuo fault and G39 fault are second order fault, the others are third order fault, with most of the dip angles being from 55 degree to 70 degree. These three indexes indicate that most of the main faults in the study area experienced two evolution stages, and each was fromweak to strong and became weak again.

Characteristics and evaluation of Chang 6 sandstone reservoir of Upper Triassic in Fuxian area, Ordos Basin

HUANG Long, TIAN Jingchun, XIAO Ling, WANG Feng

2008, Vol.20(1): 83–88 Abstract ( 592 ) PDF (453 KB) ( 757 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.014

Based on core observation and the data of cast thin section, scanning electron microscope, physical property, porosity and permeability analysis, Chang 6 sandstone reservoir of Upper Triassic in Fuxian area is analyzed. The result shows that the reservoir is delta front deposit. The lithologies of the reservoirs are mainly arkose and lithic arkose and the reservoir space mainly includes primary residual intergranular pores and secondary intergranular dissolved pores with poor physical property, high displacement pressure and high saturation median point pressure, small pore throat radius, poor pores throat sorting and fine skewness. The quality of reservoir is affected by sedimentary microfacies and diagenesis. Subaqueous distributary channel and mouth bar sand bodies are the best microfacies for reservoir development. Strong compaction and pressolution is the another factor which results in low porosity and lowpermeability. According to the physical properties of reservoir and pore structure parameters, Chang 6 sandstone reservoir is classified into four types. The type Ⅰand type Ⅱ reservoirs can be taken as the major target zones for further exploitation.

Characteristics and geological significance of seismites

YANG Shiwei, LI Jianming

2008, Vol.20(1): 89–94 Abstract ( 833 ) PDF (368 KB) ( 1092 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.015

Seismite is a type of catastrophic deposits. The characteristics and geological significance of seismites are summarized. The rock types, seismic sequences, distinguishing marks of seismites and the contrasts among seismites, tsunamites and seismoturbidites are introduced. Based on the former research, six seismic sequences are proposed, which are composed of seismites, tsunamites, seismoturbidites and background deposits. Seismites take a significant part in the studies on the interpretation of tectonic evolution, sedimentology and reservoir geology.

Study and application of seismic prestack analysis technique in Zizhou Gas Field

WANG Daxing, YU Bo, ZHANG Mengbo, SONG Chen

2008, Vol.20(1): 95–100 Abstract ( 528 ) PDF (642 KB) ( 585 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.016

The sandstone of the second member of Shanxi Formation in Zizhou Gas Field is characterized by thin reservoir and quick lateral variation. Based on the poststack seismic reservoir prediction, the method of prestack seismic reservoir prediction is studied and applied. The prediction accuracy for the effective reservoir can be improved by using prestack inversion to calculate elastic impedance and elastic parameters. The application of this technique in the reservoir prediction in Zizhou Gas Field shows that the prediction coincidence rate is raised, and that it takes a significant part in the development in Zizhou Gas Field.

Using time-frequency analysis to identify oil and water layers in array acoustic logging

ZHANG Xuetao, WANG Zhuwen, YUAN Jinghai

2008, Vol.20(1): 101–104 Abstract ( 446 ) PDF (200 KB) ( 629 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.017

Time-frequency analysis method has been applied in many fields, and it acquires a great of achievements. Choi-Williams time-frequency method is proposed for array acoustic logging signal analysis to identify different reservoirs. Choi-Williams distribution has apparent physical significance. The Choi-Williams energy distribution has different characteristics under different time and different frequency, which is applied to identify oil and water layers. Good result has been achieved.

Using NMR T2 spectrum distribution to study fractal nature of pore structure

CHEN Zhenbiao, ZHANG Chaomo, ZHANG Zhansong, LING Husong, SUN Baodian

2008, Vol.20(1): 105–110 Abstract ( 572 ) PDF (318 KB) ( 481 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.018

It is a newmethod to analyze the fractal nature of pore structure and petrophysical property by using NMR T2 spectrum distribution. Based on the former study, the fractal nature of the medium-high porosity and permeability reservoir is analyzed, and then the applicability and reliability of this method are discussed in low porosity and low permeability reservoir, finally, the application effect of this method in medium-high porosity and permeability reservoir is compared with the effect in lowporosity and lowpermeability reservoir. The result shows that it could determine the fractal nature of pore structure exactly and calculate the fractal dimension by using NMR T2 spectrumdistribution. The fractal dimension calculated by this method could characterize the petrophysical property closely and provide reference for reservoir characteristics research and reservoir classification.

Two types of stress sensitivity mechanisms for reservoir rocks:Being favorable for oil recovery

LI Chuanliang, TU Xingwan

2008, Vol.20(1): 111–113 Abstract ( 591 ) PDF (209 KB) ( 616 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.019

There exist two typical deformations for reservoir rocks: primary deformation and structural one. Accordingly, there are two types of stress sensitivity for reservoir rocks. Based on the research, the stress sensitivity of reservoir rocks caused by primary deformation is quite weak, and it can be neglected in the production practice of reservoir development. However, the stress sensitivity of reservoir rocks caused by structural deformation is quite strong, which can not only reduce the production rate of reservoir, but also maintain the reservoir pressure properly and increase the production rate of oil. The stress sensitivity of reservoir rocks is quite favorable for oil recovery.

Discussion on stratigraphic-lithologic reservoirs exploration in the aspect of the research history of reservoirs

ZHANG Houfu, XU Zhaohui

2008, Vol.20(1): 114–123 Abstract ( 546 ) PDF (667 KB) ( 1049 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.020

On the basis of clarifying the conception of reservoirs, according to the history of the research on reservoirs, it is an inevitable course of history that stratigraphic-lithologic reservoirs are regarded as an important part in the petroleum prospecting. The category, genesis and prospecting features of stratigraphic-lithologic reservoirs are summarized, and three typical examples are analyzed.

Reconstruction of Tarim-Yangtze Paleocontinent model and its implications for the generation of inorganic petroleum

LUO Zhili, ZHANG Jinglian, SHI Lanting

2008, Vol.20(1): 124–128 Abstract ( 446 ) PDF (182 KB) ( 549 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.021

According to the isotope chronology, petrology, tectonics and paleontology, the geological characteristics of Yangtze paleo-plate and Tarim paleo-plate are discussed. The study results show that the Yangtze paleo-plate was close to Tarim paleo-plate from the Neoproterozoic to the Permian and became a paleo-continent named Tarim- Yangtze Paleocontinent. Under the action of “Emei mantle plume”and the extension of “Emei Taphrogeny”, the Tarim-Yangtze Paleocontinent diverged and separated. The relation between the mantle plume and the generation of inorganic petroleum is discussed. It shows that Songpan-Ganzi folded belt in Sichuan province is a favorable target for a breakthrough of petroleumexploration.

Cultivation of explorer’s comprehensive quality(Ⅱ)———Scientific way of thinking

ZHANG Xia

2008, Vol.20(1): 129–133 Abstract ( 418 ) PDF (139 KB) ( 285 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.01.022

Scientific thinking is a kind of rational thinking which is based on fact and logic. The exploration geologists need to cultivate scientific spirit and scientific style of work and improve their scientific thinking capability in order to improve the research level. It is necessary to attach importance to the understanding of concept, establish real and practical style of study, improve the research capability, subdivide the subject investigated, strengthen comprehensive research and cultivate strict style of work for the cultivation of scientific thinking capability.